Range rate based stopped detection

ABSTRACT

Methods, devices, and systems are described for determining whether a mobile device is in a stopped state based at least in part on round trip time (RTT) measurements between the device and at least one access point. The stopped state determination may be based on RTT measurements alone, or on RTT measurements in combination with other positioning and movement measurements. Further, filtering such as particle and Kalman filtering may be used to improve determination of whether the device is in a stopped state.

FIELD

Aspects of the disclosure relate to determining whether a device is in astopped state, and in particular, to using round trip time (RTT)measurements for at least a portion of a determination as to whether amobile device is in a stopped state.

BACKGROUND

Mobile devices such as smart phones, tablets, laptop computers, andother such electronic devices have developed to include additionalfunctionality for determining the location of the device. While suchlocation functionality may serve for providing location services anddirection services, additional functionality may be derived from theelements used to implement location services. One potential piece ofinformation that may be derived from location functionality is whether adevice is in a stopped state where a user is not moving, or is movingonly a small amount. This information may be used in a variety of waysby the device.

A known method of stopped detection is the use of an accelerometer tomeasure device movement, with a stopped state based on the measurementof the accelerometer. Such measurements, however, are vulnerable tosudden movements and device shaking. There is therefore a need forimproved systems and methods for determining a device stopped state.

BRIEF SUMMARY

Embodiments described herein include systems, methods, devices, andcomputer-readable media for determining whether a device is in a stoppedstate using RTT measurements.

One embodiment may be a method comprising: collecting a plurality ofround trip time (RTT) measurements between a mobile device and at leastone access point (AP); analyzing the plurality of RTT measurements; anddetermining that the mobile device is in a stopped state based, at leastin part, on the analyzing of the plurality of RTT measurements betweenthe mobile device and the at least one AP.

Additional embodiments of such a method may function where the pluralityof RTT measurements comprise a first plurality of RTT measurementsbetween the mobile device and a first AP and a second plurality of RTTmeasurements between the mobile device and a second AP.

Additional embodiments of such a method may function where determiningthat the mobile device is in the stopped state comprises independentlyanalyzing the first plurality of RTT measurements and the secondplurality of RTT measurements, and determining that the mobile device isin the stopped state if both the first plurality of RTT measurements andthe second plurality of RTT measurements independently identify that themobile device is in the stopped state.

Additional embodiments of such a method may further comprise collectingmovement data from a plurality of data sources; where determining thatthe mobile device is in the stopped state comprises determining that auser identified threshold number of the plurality of data sources andthe RTT measurements identify the mobile device as in the stopped state.

Additional embodiments of such a method may function where determiningthat the mobile device is in the stopped state comprises determiningthat a change in RTT measurement is below a predetermined threshold fora first period of time or where determining that the mobile device is inthe stopped state further comprises filtering the plurality of RTTmeasurements between the mobile device and the at least one AP.

Additional embodiments of such a method may function where the RTTmeasurements are filtered using a free particle filter or wheredetermining whether the mobile device is in the stopped state is furtherbased at least in part on at least one global navigation satelliteservice (GNSS) measurement.

Additional embodiments of such a method may function where thedetermining whether the mobile device is in the stopped state is furtherbased at least in part on received signal strength indication (RSSI)measurements between the mobile device and the at least one AP or wherethe determining whether the mobile device is in the stopped state isfurther based on an analysis of a correlation between the RSSImeasurements and the RTT measurements.

Additional embodiments of such a method may function where thedetermining whether the mobile device is in the stopped state is furtherbased at least in part on sensor data from an accelerometer of themobile device during a first time period or where the determiningwhether the mobile device is in the stopped state is further based on anoutput of a Kalman filter using the sensor data, the RSSI measurements,and the RTT measurements.

Additional embodiments of such a method may function where determiningthat the mobile device is in the stopped state comprises determining,based at least in part on the plurality of RTT measurements, that aposition of the mobile device remains within a threshold area during afirst period of time. Still further embodiments of this embodiment mayfunction where threshold area is based at least in part on a known noisevalue associated with RTT measurements involving the at least one AP;where the threshold area is associated with a user selected or otherwisepredetermined displacement value; where the user selected orpredetermined displacement value is 5 cm or where the user selecteddisplacement value is 5 m. In certain embodiments, the predetermineddisplacement value is received as a user input at the mobile device.

Additional embodiments of such a method may function where initiatingcollection of the plurality of RTT measurements in response to a signalfrom a tracking device that is separate from the mobile device.Additional embodiments may further involve receiving, at the trackingdevice, a request for the stopped state from a position trackingmanagement entity; and communicating the signal from the tracking deviceto the mobile device in response to receiving the

Another alternative embodiment may be a mobile device comprising: meansfor collecting a plurality of round trip time (RTT) measurements betweenthe mobile device and at least one access point (AP); means foranalyzing the plurality of RTT measurements; and means for determiningthat the mobile device is in a stopped state based, at least in part, onthe analyzing of the plurality of RTT measurements between the mobiledevice and the at least one AP.

Additional embodiments of such a mobile device may further include meansfor collecting a plurality of movement measurements in addition to theRTT measurements; and means for filtering the plurality of RTTmeasurements and the plurality of movement measurements. Additionalembodiments of such a mobile device may further include means forcommunicating results of the determining that the mobile device is inthe stopped state to a user.

Another alternative embodiment may be mobile device comprising: aprocessor; a wireless transceiver coupled to the processor; and a memorycoupled to the processor and comprising a round trip time (RTT)positioning module which causes the processor to: collect a plurality ofround trip time (RTT) measurements between the mobile device and atleast one access point (AP); and determine that the mobile device is ina stopped state by analyzing the plurality of RTT measurements betweenthe wireless transceiver and the at least one AP.

Additional embodiments of such a mobile device may further include auser input module connected to the processor, wherein the RTTpositioning module further causes the processor to: display a userinterface on the mobile device; and accept a predetermined threshold asa user selected threshold via the user interface.

Additional embodiments of such a mobile device may further functionwhere the RTT positioning module further causes the processor to:initiate collection of the plurality of RTT measurements in response toa request from an application module for the stopped state.

Another embodiment may be a non-transitory computer-readable instructionmedium comprising instructions that, when executed by a processorcoupled to the non-transitory computer-readable instruction medium,cause a mobile device comprising the processor to: collect a pluralityof round trip time (RTT) measurements between the mobile device and atleast one access point (AP); and determine that the mobile device is ina stopped state by analyzing the plurality of RTT measurements betweenthe mobile device and the at least one AP.

Additional embodiments may function where the instructions further causethe mobile device comprising the processor to: identify a plurality ofAPs; and select the at least one AP from the plurality of APs.Additional embodiments may function where the at least one AP isselected from the plurality of APs based on a signal quality of the atleast one AP. Additional embodiments may function where the at least oneAP is selected from the plurality of APs based on a position of the atleast one AP. Additional embodiments may function where the plurality ofRTT measurements between the mobile device and at least one AP arecollected without determining a processing delay associated with the AP.

Another embodiment may be a method comprising initiating, by a trackingsystem computer, a plurality of RTT measurements between a mobile deviceand at least one access point; analyzing the plurality of RTTmeasurements, and determining that the mobile device is in a stoppedstate based, at least in part, on the analyzing of the plurality of RTTmeasurements between the mobile device and the at least one AP.Additional embodiments may function where the tracking system computerreceives the plurality of RTT measurements from the mobile device, andwherein the tracking system computer analyzes the plurality of RTTmeasurements and determines that the mobile device is in the stoppedstate. In still further embodiments, the tracking system computer maycommunicate the determination that the mobile device is in the stoppedstate to the mobile device. In further additional embodiments, thetracking system computer may initiate the plurality of RTT measurementsby communicating with the at least one AP. In further embodiments, thetracking system computer may receive the plurality of RTT measurementsfrom the at least one AP. In still further embodiments, the trackingsystem computer may initiate SPS measurements of a local device, anddetermine that the mobile device is in a stopped state using the SPSmeasurements in addition to the plurality of RTT measurements.

Further embodiments will be apparent in view of the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of variousembodiments may be realized by reference to the following figures. Inthe appended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 describes one embodiment of a system for measuring whether adevice is in a stopped state using RTT measurements;

FIG. 2A describes aspects of one embodiment of a method for measuringwhether a device is in a stopped state using RTT measurements;

FIG. 2B describes aspects of one embodiment of a method for measuringwhether a device is in a stopped state using RTT measurements;

FIG. 3 describes one embodiment of RTT data that may be used inaccordance with various embodiments;

FIG. 4 is one potential example of a mobile device for use withdifferent embodiments;

FIG. 5 describes one embodiment of a method for measuring whether adevice is in a stopped state using RTT measurements;

FIG. 6 describes one embodiment of a system for measuring whether adevice is in a stopped state using RTT measurements;

FIG. 7 is one potential implementation of a computer device according tocertain embodiments; and

FIG. 8 is one potential implementation of a networked computer systemaccording to certain embodiments.

DETAILED DESCRIPTION

Aspects of the disclosure relate to networked computing technologies andlocation measurements. In particular, aspects of the disclosure relateto systems, methods, apparatus, and computer-readable media fordetermining whether a device is in a stopped state using RTTmeasurements.

Embodiments described herein provide for the use of RTT measurements ordeltaRTT measurements between a mobile device and an access point (AP)to determine when a device is moving relative to the stationary AP. A“stopped state” is a device state which is selected based on an analysisof movement data. A device need not be absolutely stationary in order tobe considered in a stopped state. Instead, a stopped state may beconsidered an estimate of device environment. For example, a device maybe in a stopped state if a user is standing and shifting weight betweenfeet. Even though the device may be moving, the movement may be smallcompared to walking or running.

To determine a stopped state, a number of APs may be used in conjunctionwith measurements for a single device. Because RTT measurements will notchange when a device is moving in a circle around an AP, the use ofmultiple APs may provide improved reliability for the determination ofwhether a device is stopped. Further, additional embodiments may useother sources of movement information from local device measurementssuch as accelerometer measurements, as well as from other locationservices such as satellite-based global positioning services. Any ofthese measurements may be combined with RTT measurements to determinewhether the device is in a stopped state, and may further be filteredwith various filtering embodiments described herein to additionallyimprove the performance of a system to determine a stopped state for amobile device.

As mentioned above, embodiments described herein use RTT measurements.Round trip time measurements are a pseudo-range measurement based on thetime elapsed between the departure time of a probe packet sent by amobile device and the reception time of the acknowledgment sent by theAP. Such an RTT measurement is approximately equal to twice thetime-of-flight of light between the mobile and the AP, plus a processingdelay at the AP. For APs with MAC-layer processing in hardware, theprocessing delay is approximately constant. The delay time for aparticular AP can either be pre-determined via factory calibration orlearnt over time during the course of positioning. For embodimentsdescribed herein that are concerned with a change in RTT measurement,the processing delay may be ignored as long as any change in theprocessing delay is small relative to a movement threshold fordetermining a stopped state. If additional distance measurements areinvolved in certain embodiments, the delay may be subtracted out to getan approximate estimate of the distance between the mobile and the AP.The estimate will be approximate due to errors in processing delayestimation, as well as due to issues of multipathing in indoorpropagation.

FIG. 1 describes a basic system 100 for determining a stopped state fora mobile device 110. FIGS. 2A and 2B describe corresponding methods thatmay be used with such a system 100. The system 100 includes both themobile device 110 and at least one AP 120, with APs 120 a, 120 b, and120 n shown. Any number of APs may be used. In certain embodiments, amobile device may have a threshold number of APs, such that if thedevice is within range of more than the threshold number of APs, thedevice will select among the available APs to determine which APs to usefor RTT measurements.

Once the system is operating, mobile device 110 will take repeated RTTmeasurements, or change in RTT (deltaRTT) measurements with the selectedAPs. This is reflected in 222 of FIGS. 2A and 2B as collecting aplurality of RTT measurements between a mobile device 110 and at leastone AP 120. As shown in FIG. 1, the RTT measurement occurs over an RTTmeasurement path, with RTT measurement paths 122 a, 122 b, and 122 nfrom mobile device 110 to respective APs 120 a, 120 b, and 120 n.

The measurement of a change in RTT from the mobile device to an APessentially only measures the radius of a circle from each AP to themobile device. This may also be considered as the change in length of avector from each AP to the corresponding mobile device. Considering theAPs of FIG. 1, if mobile device 110 is moving toward AP 120 b whilemeasuring the change in RTT to APs 120 a and 120 n, the change in RTTfor these measurements along RTT measurement paths 122 a and 122 n willbe small. The change in RTT with measurements from mobile device 110 toAP 120 b, however, will be roughly equal to the actual movement of thedevice because the device is moving directly toward AP 120 b. Because ofthis, the best results will be achieved with a sufficient number of APssuch that the mobile device 110 will not be moving on a path thatcircles all of the measured APs. In certain embodiments, informationabout the actual location of the APs may be used to ensure that the bestAPs are selected for RTT measurements.

In 204 of FIG. 2A, the data collected as part of the RTT measurements isanalyzed. This analysis may include various types of filtering andprocessing such as particle or Kalman filtering. In 206, a determinationis made that the device is in a stopped state based at least in part onthe analysis of the plurality of RTT measurements.

FIG. 2B provides additional details which may be included in certainembodiments. 202 of FIG. 2B is the same as 202 of FIG. 2A, where RTTmeasurements are collected. In 224 of FIG. 2B, the data collected aspart of the RTT measurements is used to determine a change in RTT. Thisis used for determining that the mobile device is in a stopped state byanalyzing the plurality of RTT measurements between the mobile device110 and the at least one AP 120. While in the simplest embodiment, thisdetermination of a stopped state may be based purely on the change inRTT measured from the mobile device 110 to at least one AP 120, variousoptional alternatives may be incorporated into certain embodimentsdescribed by 224 a-c.

As illustrated by 224 a, a threshold may be used for determination ofwhat is meant by a “stopped state.” In certain embodiments, thisthreshold may be determined by a user selection in an interface of themobile device. Such a threshold may be any static value compatible withthe signal strength of the AP and the sensitivity of the RTTmeasurement. Non-limiting examples may be 5 cm of absolute displacementover 3 seconds, 5 m of displacement over 10 seconds, 10 m of absolutedisplacement with no set time restriction, or any other such threshold.In alternative embodiments, the threshold may be a dynamic value basedon the number of APs available for RTT measurements, or some otherenvironmental factor associated with the mobile device 110 during RTTmeasurement such as the noise associated with a measurement. Asillustrated by 224 b, RTT data may be combined with a variety of othermovement data. Examples of such additional data may be GNSS positioningdata, received signal strength indication (RSSI) changes, accelerometermeasurements, barometer measurements for changes in height, and anyother such potential source of information. In such embodiments, theinformation may be combined to arrive at a determination of whether thedevice is in a stopped state. As illustrated by 224 c, particularfiltering may be used to improve the stopped state determination. Forexample, data may be filtered to remove outliers and prevent the stoppedstate from changing rapidly. Particle filters, Kalman filters, andmotion models may all be used for this type of improvement to the rawRTT data in order to improve or customize a system's identification of astopped state for a mobile device.

FIG. 3 then shows one potential example of RTT measurement data that maybe used in order to make a stopped state determination. FIG. 3 shows anexample of RTT measurements taken over time between a single mobiledevice such as mobile device 110 and a single AP such as AP 120 a, withraw RTT data 310 and a filtered movement estimate 320 both shown.Filtered movement estimate 320 may be created in any acceptablefiltering manner. This includes any filtering as described above in 224c. In various embodiments, the filtered movement estimate 320 may simplybe a filter applied to raw RTT data 310 to remove the signal noise. Inanother embodiment, RTT measurements and RSSI measurements may be usedin conjunction. RTT and RSSI measurements both change based on mobiledevice movement and path geometry changes for the radio frequency (RF)signals used for measurement. Because of this, RTT and RSSI measurementsparticularly may be filtered in view of these similarities.

In other embodiments, additional movement data as described above in 224b may be included in filtered movement estimate 320, and may be used todetermine when the device is in a stopped state. For example, a Kalmanfilter or linear quadratic estimation may be used with a plurality ofdifferent sets of data for movement over time. Such a filter may be usedin one potential embodiment with RTT measurements, RSSI measurements,acceleration data, and tuning parameters to create an estimate ofmovement. A threshold may be applied to the output of the Kalman filterin order to determine whether the device is in a stopped state.

In certain embodiments, a threshold may then be set at a given time,with a stopped state elected as long as the filtered movement estimate320 does not change more than the threshold amount. In furtherembodiments, the threshold amount may be set to change over time, suchthat the mobile device is considered to be in a stopped state as long asthe maximum variation of the filtered movement estimate 320 does notexceed a threshold amount over a particular time frame. In still furtherembodiments, any other static or dynamic threshold may be used based ona user selection or a system setting in order to identify a stoppedstate of the device.

FIG. 4 shows one potential implementation of a mobile device 400 thatmay be similar to mobile device 110 of FIG. 1. Further, mobile device400 may also implement processing for initiating RTT measurements,deltaRTT measurements, and other measurements that may be used todetermine a stopped state according to the embodiments described herein.Additional details of such processes may be initiated and managed by RTTpositioning module 421. In certain of such embodiments, the entireprocess of collecting RTT data and analyzing the data to determine thatmobile device 400 may be performed by mobile device 400 with nospecialized processing from any other device. In alternate embodiments,the RTT measurements may be remotely imitated by a positioning serverand created in conjunction with RTT positioning module 421 and remotenetworked elements as described in FIG. 6.

In the embodiment shown at FIG. 4, mobile device 400 includes processor410 configured to execute instructions for performing operations at anumber of components and can be, for example, a general-purposeprocessor or microprocessor suitable for implementation within aportable electronic device. Processor 410 is communicatively coupledwith a plurality of components within mobile device 400. To realize thiscommunicative coupling, processor 410 may communicate with the otherillustrated components across a bus 440. Bus 440 can be any subsystemadapted to transfer data within mobile device 400. Bus 440 can be aplurality of computer buses and include additional circuitry to transferdata.

Memory 420 may be coupled to processor 410. In some embodiments, memory420 offers both short-term and long-term storage and may in fact bedivided into several units. Memory 420 may be volatile, such as staticrandom access memory (SRAM) and/or dynamic random access memory (DRAM),and/or non-volatile, such as read-only memory (ROM), flash memory, andthe like. Furthermore, memory 420 can include removable storage devices,such as secure digital (SD) cards. Thus, memory 420 provides storage ofcomputer-readable instructions, data structures, program modules, andother data for mobile device 400. In some embodiments, memory 420 may bedistributed into different hardware modules.

In some embodiments, memory 420 stores a plurality of applicationmodules 421 and 424, which may be any number of applications 424. RTTpositioning module 421 may work in conjunction with any number of otherapplications 424 as part of a device which determines a stopped state.Applications as stored in a non-transitory memory such as memory 420contain particular instructions to be executed by processor 410. Inalternative embodiments, other hardware modules 401 may additionallyexecute certain applications 424 or parts of applications. In certainembodiments, memory 420 may additionally include secure memory, whichmay include additional security controls to prevent copying or otherunauthorized access to secure information such as secure locations ofbases stations that is not public or not expected to be shared outsideof a secure environment.

In some embodiments, memory 420 includes an operating system 423.Operating system 423 may be operable to initiate the execution of theinstructions provided by application modules and/or manage otherhardware modules 401 as well as interfaces with communication moduleswhich may use wireless transceiver 412 and to receive information fromlink 416 via antenna. Operating system 423 may be adapted to performother operations across the components of mobile device 400 includingthreading, resource management, data storage control and other similarfunctionality.

In additional embodiments wireless transceiver 412 may receiveinformation from link 416 via antenna 414 which may be passed directlyto position/velocity hardware 430 which may include specializedhardware, software, or firmware modules for RTT measurements, Dopplermeasurements, position determination, acceleration determination, orvelocity determination. In alternative embodiments, signals fromantennas may be communicated to a memory 420 for later access andprocessing by processor 410 executing RTT positioning module 421 todetermine a stopped state in accordance with the embodiments describedherein.

Additional embodiments may also include satellite power system (SPS)antenna 444 coupled to SPS transceiver 442 to receive satellite signalsover link 446. Such signals may be used to improve positioning inconjunction with other positioning signals described herein. In stillfurther embodiments, specialized modules may implement communicationswhich are integrated with RTT measurements. For example, in certainembodiments, the wireless transceivers may receive signals associatedwith a particular communications standard. Such signals may includeknown standard reference signals which may provide standardized non-datareference signals which may be adapted for assistance in determiningwhether a device is in a stopped state in accordance with otherpositioning measurements. Certain standards, for example, non-datareference signals such as a Positioning Reference Signal (PRS), a CellSpecific Reference Signal (CRS), a primary synchronization signal (PSS),or a secondary synch signal (SSS). PRS, CRS, PSS, SSS signals, as onepotential example, are illustrated by standard 3GPP 36.211 V10.0.0(2011-01). Other communication systems such as code division multipleaccess systems may use pilot reference signals that may be incorporatedwith positioning systems for use in determining whether mobile device400 is in a stopped state. Other signals may be received as part of animplementation of GNSS or satellite positioning, or provided as part ofa communication system such as a clock frequency referenced off of a WANsignal. In various embodiments, mobile device 400 may include GNSS clockcircuitry, support hardware, and other functionality.

In some embodiments, mobile device 400 includes a plurality of otherhardware modules 401. Each of other hardware modules 401 is a physicalmodule within mobile device 400. However, while each of hardware modules401 is permanently configured as a structure, a respective one ofhardware modules 401 may be temporarily configured to perform specificfunctions or temporarily activated. A common example is an application424 that may program a camera module (i.e., hardware module) for shutterrelease and image capture. A respective one of hardware modules 401 canbe, for example, an accelerometer, a Wi-Fi transceiver, a satellitenavigation system receiver (e.g., a GPS module), a pressure module, atemperature module, an audio output and/or input module (e.g., amicrophone), a camera module, a proximity sensor, an alternate lineservice (ALS) module, a capacitive touch sensor, a near fieldcommunication (NFC) module, a Bluetooth® transceiver, a cellulartransceiver, a magnetometer, a gyroscope, an inertial sensor (e.g., amodule that combines an accelerometer and a gyroscope), an ambient lightsensor, a relative humidity sensor, or any other similar module operableto provide sensory output and/or receive sensory input. In someembodiments, one or more functions of the hardware modules 401 may beimplemented in software, firmware, or any combination of such.

In certain embodiments, hardware modules 401 and/or position/velocityhardware 430 may include specialized functionality for determining thevelocity of mobile device 400 as part of an embodiment for determining astopped state of mobile device 400. Such components may beaccelerometers, inertial sensors, gyroscopes, or other such devicesdescribed above which are configured to work alone or in combination toprovide accurate velocity measurements in conjunction with correspondingRTT measurements and RTT positioning module 421.

Mobile device 400 may include a component such as a wirelesscommunication module which may integrate antenna 414 and wirelesstransceiver 412 with any other hardware, firmware, or software necessaryfor wireless communications. Such a wireless communication module may beconfigured to receive signals from various devices such as data sourcesvia networks and access points. In addition to other hardware modules401 and applications 424 in memory 420, mobile device 400 may have adisplay module 403 and a user input module 404. Display module 403graphically presents information from mobile device 400 to the user.This information may be derived from one or more applications 424, oneor more hardware modules 401, a combination thereof, or any othersuitable means for resolving graphical content for the user (e.g., byoperating system 423). Display module 403 can be liquid crystal display(LCD) technology, light-emitting polymer display (LPD) technology, orsome other display technology. In some embodiments, display module 403is a capacitive or resistive touch screen and may be sensitive to hapticand/or tactile contact with a user. In such embodiments, the displaymodule 403 can comprise a multi-touch-sensitive display. Display output403 may then be used to settings, output information, or other userinterface components of RTT positioning module 421. In variousembodiments, when a determination is made that the mobile device 400 isin a stopped state, as described by element 206 of FIG. 2A, thisdetermination may be output on display output 403. Alternatively, mobiledevice 400 may have a set of interface or display systems which arealtered, so that a particular user interface is displayed following orduring a determination that mobile device 400 is in a stopped state. Aspart of the stopped state determination, mobile device may identify thecurrent interface being presented on display output 403, and if thecurrent interface is not the interface associated with a stopped state,aspects of RTT positioning module 421 or another application 424 mayautomatically adjust the information presented on display output 403 toa stopped state interface.

Additional potential embodiments of a mobile device may further comprisevarious portions of computing devices as are detailed below with respectto FIG. 7 and networks as detailed in FIG. 8.

FIG. 5 now shows one potential additional method of stopped stateddetection. The method of FIG. 5 may particularly require a plurality ofAPs in order to determine if a device is in a stopped state in atwo-dimensional single floor area. In further alternative embodimentswith a multi-level environment with APs on multiple floors, three APsmay be required to determine if the mobile device is moving in threedimensions. This may include movement on escalators, elevators, and upand down movement. In some embodiments, RTT measurements may be used fortwo-dimensional movement on a single floor of an environment, with datafrom other sensors such as a barometer used for determination of up anddown movement.

In 502, a method begins with repeatedly measuring, over a first timeperiod, a round trip time (RTT) between a mobile device and a firstnetwork access point to create a first RTT data set. In 504, the methodcontinues with identifying a first threshold associated with the RTTbetween the mobile device and the first network access point. In such anembodiment, the threshold may be associated with a single set ofmeasurements between a mobile device such as mobile device 110 and aparticular AP such as AP 120 a. 506 then involves repeatedly measuring,over the first time period, a RTT between the mobile device and a secondnetwork access point to create a second RTT data set. 508 involvesidentifying a second threshold associated with the RTT between themobile device and the second network access point. These measuring andthreshold identification steps may be repeated for any number of sets ofRTT measurements for different APs. 510 involves analyzing the first RTTdata set in real-time or near real-time as the first RTT data set iscreated to identify changes in the RTT between the mobile device and thefirst network access point which are above the first threshold. This mayenable a device to present a stopped state result to a user of themobile device as the determination is made. 512 similarly involvesanalyzing the second RTT data set in real-time or near real-time as thesecond RTT data set is created to identify changes in the RTT betweenthe mobile device and the second network access point which are abovethe second threshold. This analysis of the first and second sets of RTTdata may then be used in 514 in determining whether the mobile device isin a stopped state at least in part by determining when the changes inthe RTT between the mobile device and the first network access point arenot above the first threshold at the same time that the changes in theRTT between the mobile device and the second network access point arenot above the second threshold.

In other embodiments, any number of APs may be used, and any combinationof multiple thresholds on a per AP level, a per measurement type level,an overall filtering combination level. This may result in conflictinginformation on determination of a stopped state. In certain embodiments,rules may be set for priority determinations based on more reliablemeasurements. In other embodiments, any determination that a device isnot in a stopped state may cause the device to determine that it is notin a stopped state.

FIG. 6 is a block diagram illustrating an exemplary architecture of awireless system which includes a mobile device 601 and a tracking system1000. In certain embodiments, tracking system 1000 may work inconjunction with mobile device 601 to determine if device 601 is in astopped state. The depicted geometry may be adapted to perform any oneof the exemplary flow diagrams of FIG. 2A-B or 5, or any number of otherprocesses within the scope of this disclosure. One skilled in the artwould understand that FIG. 6 presents one combination and ordering ofthe blocks. Various other combinations and orderings of the blockspresented in FIG. 6 will be readily apparent to those skilled in the artwithout departing from the spirit or scope of the disclosure.

In one aspect, the mobile device 601, for example, comprises an LDC(“Low Duty Cycle”) transceiver. In another aspect, the mobile device 601may also comprise a mobile phone, a mobile station (MS), user equipment(UE), a personal digital assistant (PDA), a personal navigation device(PND, a tablet, a phablet, a laptop, or any other mobile computingdevice. This list is by example and is not limiting in any way.Selection of the mobile device 601 is a system parameter that may beselected by the user, another operator or the system designer.

In one aspect, the tracking system 1000 represents a wireless mobiledevice capable of storing and executing applications, such that it maybe a mobile device used to determine that another mobile device is in astopped state. One of ordinary skill in the art would recognize that thetracking system 1000 and its configuration as shown in FIG. 6 could alsobe the configuration of the mobile device 601. In another aspect, thetracking system 1000 is an LDC transceiver.

In one example, the tracking system 1000 comprises an SPS applicationand hardware 607 which receives the RTT which are made by device 601. Insuch an embodiment, the stopped state may not be presented to the mobiledevice 601 at all, but instead may only be presented to tracking system1000. A database manager 608, a user device database 609 and/or ahistory database 610 comprise a Database Management System (“DBMS”) 611within the tracking system 1000. The DBMS 611 provides storage for mapdisplay, data associated with the various devices and stopped statethresholds. Additionally, the DBMS 611 may also provide storage forsystem applications that run on the tracking system 1000. In oneexample, the tracking system 1000 includes an application initializationand management unit 614 and an application user interface unit 615.Working in conjunction, the application initialization and managementunit 614 and the application user interface unit 615 initialize, controland manage system applications that run on the tracking system 1000. Thetracking system 1000 may implement this functionality in any operatingsystem. One skilled in the art would understand that the operatingsystems listed are merely examples and that other operating systems maybe used without affecting the spirit and scope of this disclosure.Alternatively, all or some of the initialization, control and managementof applications may be performed separately from the specific operatingsystem present in the tracking system 1000. In one example, a trackingengine 616 is connected to the database manager 608, the applicationinitialization & management unit 614, the application user interfaceunit 615, the map application & interface unit 612 and the trackeddevice application & interface unit 613. The tracking engine 616, forexample, may determine particular thresholds for a stopped state, suchas particular movement or location areas associated with certain RTTmeasurements or deltaRTT measurements. In one aspect, the trackingengine 616, in conjunction with the internal chipset of the trackingsystem 1000, synthesizes the data obtained and displays a map to showthe movement of mobile device 601. One skilled in the art wouldunderstand that the components within the tracking system 1000 (as shownin FIG. 6) are provided only as examples. The tracking system 1000 caninclude other components not shown in FIG. 6 or not include some of thecomponents shown in FIG. 6 without departing from the spirit and scopeof the disclosure.

In one aspect, the processing unit includes one or more of thefollowing: database manager 608, user device database 609, historydatabase 610, application initialization and management unit 614,application user interface unit 615, map application and interface unit612, tracked device application and interface unit 613, tracking engine616 or SPS application and hardware 607.

As shown in FIG. 6, the mobile device 601 is connected to a mobilenetwork 604. The mobile network 604, which is used in one aspect torelay information to and from the mobile device 601, may comprise ofCDMA, TDMA, GSM or any other wireless air interfaces. Also, in oneaspect, the mobile network 604 is connected to an IP (“InternetProtocol”) network 605 and an SMS (“Short Message Service”) network 606.In other embodiments, other network connections may use means such assignal 602 operating via satellite 603 a or terrestrial source 603 b.The IP network 605 may include a plurality of APs for performing RTTmeasurements with mobile device 601. IP network 605 may also function asa system by which data is sent from one host to another host via anetwork (e.g., the Internet). The SMS network 606 sends short textmessages between devices. In one aspect, the mobile network 604 relaysdata from the mobile device 601 to the IP network 605 and the SMSnetwork 606. In another aspect, the mobile device 601 is directlyconnected to the IP network 605 and to the SMS network 606, as shown inFIG. 6. In one aspect, the tracking system 1000 is similarly connectedto the mobile network 604, the IP network 605 and/or the SMS network606. Or, the tracking system 1000 may be connected to the IP network 605and SMS network 606 through the mobile network 604. The connection ofmobile device 601 and tracking system 1000 to one or more of the mobilenetwork 604, SMS network 606 or IP network 605 allows for theflexibility of relaying information between devices.

In one example, mobile device 601 (through its RTT positioning module orother such tracking modules) is connected to the IP network 605. Mobiledevice 601 may also be connected to the mobile network 604. A MappointWeb Service 617 is also connected to the IP network 605 or the mobilenetwork 604. Stopped state data, raw RTT measurements, filtered movementestimates, or any combination thereof may be sent to the Mappoint WebService 617 which is then able to relay information from its mapdatabase 618 to the tracking system 1000. Additionally, stopped statedata can be relayed via the IP network 605 or the mobile network 604from the mobile device 601 or the position determining entity 1008 tothe tracking system 1000.

In one example, the mobile device 601 sends an SMS text message via theSMS network 606 or the mobile network 604 to the tracking system 1000 orvice versa. Alternatively, the position tracking management entity(PTME) 620 may send an SMS text message to the tracking system 1000 ormobile device 601. PTME 620 may be a third party system providingdetails, controls, or information to initiate stopped state detection orto receive stopped state information for a mobile device 601. Uponreceiving the SMS text message, the tracking system 1000 may initiate astopped state measurement on mobile device 601, and may return theresults of the stopped state measurement to the PTME 620.

FIG. 7 provides a schematic illustration of one embodiment of acomputing device 700 that can perform the methods provided by variousother embodiments such as the embodiments described by FIGS. 1-3 asdescribed herein. Elements of FIG. 7 may be used as part of any deviceor component described herein. For example, device 700 may describeaspects of APs 120 a-c, mobile device 110, tracking system 1000, mobiledevice 601, or any other communications component needed for a networkdevice or network component described herein. FIG. 7 is meant only toprovide a generalized illustration of various components, any or all ofwhich may be utilized as appropriate. FIG. 7, therefore, broadlyillustrates how individual system elements may be implemented in arelatively separated or relatively more integrated manner, and describeselements that may implement specific methods according to embodiments ofthe invention when, for example, controlled by computer-readableinstructions from a non-transitory computer-readable storage device suchas storage device(s) 725.

The computing device 700 is shown comprising hardware elements that canbe electrically coupled via a bus 705 (or may otherwise be incommunication, as appropriate). The hardware elements may include one ormore processors 710, including, without limitation, one or moregeneral-purpose processors and/or one or more special-purpose processors(such as digital signal processing chips, graphics accelerationprocessors, and/or the like); one or more input devices 715, which caninclude, without limitation, a mouse, a keyboard and/or the like; andone or more output devices 720, which can include, without limitation, adisplay device, a printer and/or the like.

The computing device 700 may further include (and/or be in communicationwith) one or more non-transitory storage devices 725, which cancomprise, without limitation, local and/or network accessible storage,and/or can include, without limitation, a disk drive, a drive array, anoptical storage device, a solid-state storage device such as a randomaccess memory (“RAM”) and/or a read-only memory (“ROM”), which can beprogrammable, flash-updateable and/or the like. Such storage devices maybe configured to implement any appropriate data stores, including,without limitation, various file systems, database structures, and/orthe like.

The computing device 700 might also include a communications subsystem730, which can include, without limitation, a modem, a network card(wireless or wired), an infrared communication device, a wirelesscommunication device and/or chipset (such as a Bluetooth device, a802.11 device, a Wi-Fi device, a WiMax device, cellular communicationfacilities, etc.), and/or similar communication interfaces. Thecommunications subsystem 730 may permit data to be exchanged with anetwork (such as the network described below, to name one example),other computer systems, and/or any other devices described herein. Amobile device such as mobile device 400 may thus include othercommunication subsystems in addition to those including wirelesstransceiver 412.

In many embodiments, the computing device 700 will further comprise anon-transitory working memory 735, which can include a RAM or ROMdevice, as described above. The computing device 700 also can comprisesoftware elements, shown as being currently located within the workingmemory 735, including an operating system 740, device drivers,executable libraries, and/or other code, such as one or moreapplications 745, which may comprise computer programs provided byvarious embodiments, and/or may be designed to implement methods, and/orconfigure systems provided by other embodiments, as described herein.Merely by way of example, one or more procedures described with respectto the method(s) discussed above might be implemented as code and/orinstructions executable by a computer (and/or a processor within acomputer); in an aspect, then, such code and/or instructions can be usedto configure and/or adapt a general-purpose computer (or other device)to perform one or more operations in accordance with the describedmethods for using RTT measurements to determine a stopped state.

A set of these instructions and/or code might be stored on acomputer-readable storage medium, such as the storage device(s) 725described above. In some cases, the storage medium might be incorporatedwithin a computer system, such as computing device 700. In otherembodiments, the storage medium might be separate from a computer system(e.g., a removable medium, such as a compact disc), and/or provided inan installation package, such that the storage medium can be used toprogram, configure and/or adapt a general-purpose computer with theinstructions/code stored thereon. These instructions might take the formof executable code, which is executable by the computing device 700and/or might take the form of source and/or installable code, which,upon compilation and/or installation on the computing device 700 (e.g.,using any of a variety of generally available compilers, installationprograms, compression/decompression utilities, etc.) then takes the formof executable code. RTT positioning module 421 may thus be executablecode as described herein.

Substantial variations may be made in accordance with specificrequirements. For example, customized hardware might also be used,and/or particular elements might be implemented in hardware, software(including portable software, such as applets, etc.), or both. Moreover,hardware and/or software components that provide certain functionalitycan comprise a dedicated system (having specialized components) or maybe part of a more generic system. An activity selection subsystemconfigured to provide some or all of the features described hereinrelating to the selection of acceptable characteristics for an output 3Dimage created from multiple two-dimensional sources, and such subsystemscomprise hardware and/or software that is specialized (e.g., anapplication-specific integrated circuit (ASIC), a software method, etc.)or generic (e.g., processor(s) 710, applications 745 which may, forexample, implement any module within memory 735, etc.) Further,connection to other computing devices such as network input/outputdevices may be employed.

The terms “machine-readable medium” and “computer-readable medium,” asused herein, refer to any medium that participates in providing datathat causes a machine to operate in a specific fashion. In an embodimentimplemented using the computing device 700, various computer-readablemedia might be involved in providing instructions/code to processor(s)710 for execution and/or might be used to store and/or carry suchinstructions/code (e.g., as signals). In many implementations, acomputer-readable medium is a physical and/or tangible storage medium.Such a medium may take many forms, including, but not limited to,non-volatile media, non-transitory media, volatile media, andtransmission media. Non-volatile media include, for example, opticaland/or magnetic disks, such as the storage device(s) 725. Volatile mediainclude, without limitation, dynamic memory, such as the working memory735. Transmission media include, without limitation, coaxial cables,copper wire and fiber optics, including the wires that comprise the bus705, as well as the various components of the communications subsystem730 (and/or the media by which the communications subsystem 730 providescommunication with other devices).

Common forms of physical and/or tangible computer-readable mediainclude, for example, a floppy disk, a flexible disk, hard disk,magnetic tape, or any other magnetic medium, a CD-ROM, any other opticalmedium, punchcards, papertape, any other physical medium with patternsof holes, a RAM, a PROM, EPROM, a FLASH-EPROM, any other memory chip orcartridge, a carrier wave as described hereinafter, or any other mediumfrom which a computer can read instructions and/or code. Any such memorymay function as memory 735 or as secure memory if structured to maintainsecurity of stored content.

The communications subsystem 730 (and/or components thereof) generallywill receive the signals, and the bus 705 then might carry the signals(and/or the data, instructions, etc. carried by the signals) to theworking memory 735, from which the processor(s) 710 retrieves andexecutes the instructions. The instructions received by the workingmemory 735 may optionally be stored on a non-transitory storage device725 either before or after execution by the processor(s) 710.

Thus, in certain embodiments, computing device 700 may be configured toor may operate to collect a plurality of RTT measurements with at leastone AP; analyze the plurality of RTT measurements; and determining thatthe computing device 700 is in a stopped state based, at least in part,on the analyzing of the plurality of RTT measurements between thecomputing device 700 and the at least one AP.

In various embodiments as described herein, computing devices may benetworked in order to communicate information. For example, mobiledevice 400 may be networked to receive information as described above.Additionally, each of these elements may engage in networkedcommunications with other devices such as web servers, databases, orcomputers which provide access to information to enable applications vianetwork.

FIG. 8 illustrates a schematic diagram of a system 800 of networkedcomputing devices that can be used in accordance with variousembodiments to enable systems such as system 800 or other systems thatmay RTT measurements to identify a device stopped state. For example, invarious embodiments, the output location information may be communicatedvia networked computers to one or more databases as described by system800. The system 800 can include one or more user computing devices 805.The user computing devices 805 can be general-purpose personal computers(including, merely by way of example, personal computers and/or laptopcomputers running any appropriate flavor of Windows® and/or Mac OS®operating systems) and/or workstation computers running any of a varietyof commercially-available UNIX® or UNIX-like operating systems. Theseuser computing devices 805 can also have any of a variety ofapplications, including one or more applications configured to performmethods of the invention, as well as one or more office applications,database client and/or server applications, and web browserapplications. Alternatively, the user computing devices 805 can be anyother electronic device, such as a thin-client computer,Internet-enabled mobile telephone, and/or personal digital assistant(PDA), capable of communicating via a network (e.g., the network 810described below) and/or displaying and navigating web pages or othertypes of electronic documents. Although the exemplary system 800 isshown with three user computing devices 805 a-c, any number of usercomputing devices can be supported.

Certain embodiments of the invention operate in a networked environment,which can include a network 810. The network 810 can be any type ofnetwork familiar to those skilled in the art that can support datacommunications using any of a variety of commercially-availableprotocols, including, without limitation, TCP/IP, SNA, IPX, AppleTalk®,and the like. Merely by way of example, the network 810 can be a localarea network (“LAN”), including, without limitation, an Ethernetnetwork, a Token-Ring network and/or the like; a wide-area network(WAN); a virtual network, including, without limitation, a virtualprivate network (“VPN”); the Internet; an intranet; an extranet; apublic switched telephone network (“PSTN”); an infrared network; awireless network, including, without limitation, a network operatingunder any of the IEEE 802.11 suite of protocols, the Bluetooth protocolknown in the art, and/or any other wireless protocol; and/or anycombination of these and/or other networks. Network 810 may includeaccess points such as an access point 120 for enabling access to network810 by various computing devices.

Embodiments of the invention can include one or more servers 860. Eachof the servers 860 may be configured with an operating system,including, without limitation, any of those discussed above, as well asany commercially (or freely) available server operating systems. Each ofthe servers 860 may also be running one or more applications, which canbe configured to provide services to one or more user computing devices805 and/or other servers 860.

Merely by way of example, one of the servers 860 may be a web server,which can be used, merely by way of example, to process requests for webpages or other electronic documents from user computing devices 805. Theweb server can also run a variety of server applications, including HTTPservers, FTP servers, CGI servers, database servers, Java® servers, andthe like. In some embodiments of the invention, the web server may beconfigured to serve web pages that can be operated within a web browseron one or more of the user computing devices 805 to perform methods ofthe invention. Such servers may be associated with particular IPaddresses, or may be associated with modules having a particular URL,and may thus store secure navigation modules which may interact with amobile device such as mobile device 400 to provide secure indications ofgeographic points as part of location services provided to mobile device400.

In accordance with further embodiments, one or more servers 860 canfunction as a file server and/or can include one or more of the files(e.g., application code, data files, etc.) necessary to implementmethods of various embodiments incorporated by an application running ona user computing device 805 and/or another server 860. Alternatively, asthose skilled in the art will appreciate, a file server can include allnecessary files, allowing such an application to be invoked remotely bya user computing device 805 and/or server 860. It should be noted thatthe functions described with respect to various servers herein (e.g.,application server, database server, web server, file server, etc.) canbe performed by a single server and/or a plurality of specializedservers, depending on implementation-specific needs and parameters.

In certain embodiments, the system can include one or more databases820. The location of the database(s) 820 is discretionary: merely by wayof example, a database 820 a might reside on a storage medium local to(and/or resident in) a server 860 a (and/or a user computing device805). Alternatively, a database 820 b can be remote from any or all ofthe user computing devices 805 or servers 860 a,b, so long as thedatabase 820 b can be in communication (e.g., via the network 810) withone or more of these. In a particular set of embodiments, a database 820can reside in a storage-area network (“SAN”) familiar to those skilledin the art. (Likewise, any necessary files for performing the functionsattributed to the user computing devices 805 or servers 860 can bestored locally on the respective computer and/or remotely, asappropriate.) In one set of embodiments, the database 820 can be arelational database, such as an Oracle® database, that is adapted tostore, update, and retrieve data in response to SQL-formatted commands.The database might be controlled and/or maintained by a database server,as described above, for example. Such databases may store informationrelevant to levels of security.

For example, in one potential embodiment, server 860 a may be a serverthat stores a base station almanac in a database. Mobile devicespracticing various embodiments as described herein may communicate thelocations of one or more base stations to such a database via a networksuch as network 810. When the server receives the base station locationinformation, the server may determine if any other information isalready stored relating to the location of the particular base station.If there is no information about the base station in the database, a newentry may be created for the base station almanac with the base stationlocation from the mobile device. If an entry is already present for theparticular base station, a variety of different uses may be made of theinformation. In certain embodiments, the new information may be used toverify the previous information is correct. In other embodiments, if thenew information conflicts with the previous information, a flag may beset that further information is needed.

In other alternative embodiments, the mobile device such as computingdevice 805 b or computing device 805 c may query such a database beforemeasuring the base station location. A measurement may be taken only ifno information is currently in the database. In still furtherembodiments, the mobile device may both query the database and take ameasurement, but the measurement may only be sent to the database if themobile device receives a message that there is no current base stationlocation stored, or if the currently stored base station informationconflicts with the measurement made with the mobile device by more thana threshold amount.

The base station location sent to the server may be relative coordinateinformation that is sent with a reference measurement or other detailsfor the mobile device such that the server may use the supplementaldetails to determine the absolute position of the base station.Alternatively, the absolute position of the base station may bedetermined by the phone, and only this absolute position may becommunicated to the server for inclusion in the base station almanac ofthe database.

Thus, in certain embodiments, a computing device such as computingdevice 805 b or computing device 805 c may communicate with a server 860via network 810 as part of a stopped state determination. For example,server 860 a may communicate with computing device 805 b to initiate aplurality of RTT measurements between computing device 805 b and atleast one access point. Any computing device 805 or server 860 on thesystem may receive the plurality of RTT measurements, analyze theplurality of RTT measurements, and determine that computing device 805 bis in a stopped state based, at least in part, on the analyzing of theplurality of RTT measurements between computing device 805 b and the atleast one AP. In various alternative embodiments, the determination maybe additionally based on other information accessed via network 810, adatabase 820, or any additional system or measurement for determiningposition.

The methods, systems, and devices discussed above are examples. Variousembodiments may omit, substitute, or add various procedures orcomponents as appropriate. For instance, in alternative configurations,the methods described may be performed in an order different from thatdescribed, and/or various stages may be added, omitted, and/or combined.Also, features described with respect to certain embodiments may becombined in various other embodiments. Different aspects and elements ofthe embodiments may be combined in a similar manner.

Specific details are given in the description to provide a thoroughunderstanding of the embodiments. However, embodiments may be practicedwithout certain specific details. For example, well-known circuits,processes, algorithms, structures, and techniques have been mentionedwithout unnecessary detail in order to avoid obscuring the embodiments.This description provides example embodiments only and is not intendedto limit the scope, applicability, or configuration of variousembodiments. Rather, the preceding description of the embodiments willprovide those skilled in the art with an enabling description forimplementing embodiments. Various changes may be made in the functionand arrangement of elements without departing from the spirit and scopeof various embodiments.

Also, some embodiments were described as processes depicted in a flowwith process arrows. Although each may describe the operations as asequential process, many of the operations can be performed in parallelor concurrently. In addition, the order of the operations may berearranged. A process may have additional steps not included in thefigure. Furthermore, embodiments of the methods may be implemented byhardware, software, firmware, middleware, microcode, hardwaredescription languages, or any combination thereof. When implemented insoftware, firmware, middleware, or microcode, the program code or codesegments to perform the associated tasks may be stored in acomputer-readable medium such as a storage medium. Processors mayperform the associated tasks. Additionally, the above elements maymerely be a component of a larger system, wherein other rules may takeprecedence over or otherwise modify the application's variousembodiments, and any number of steps may be undertaken before, during,or after the elements of any embodiment are implemented.

Having described several embodiments, it will therefore be clear to aperson of ordinary skill that various modifications, alternativeconstructions, and equivalents may be used without departing from thespirit of the disclosure.

What is claimed is:
 1. A method comprising: collecting a plurality ofround trip time (RTT) measurements between a mobile device and at leastone access point (AP); analyzing the plurality of RTT measurements; anddetermining that the mobile device is in a stopped state, including:analyzing of the plurality of RTT measurements between the mobile deviceand the at least one AP; and determining that a change in measured RTTis below a predetermined threshold for a first period of time.
 2. Themethod of claim 1 wherein the plurality of RTT measurements comprise afirst plurality of RTT measurements between the mobile device and afirst AP and a second plurality of RTT measurements between the mobiledevice and a second AP.
 3. The method of claim 2 wherein determiningthat the mobile device is in the stopped state comprises independentlyanalyzing the first plurality of RTT measurements and the secondplurality of RTT measurements, and determining that the mobile device isin the stopped state if both the first plurality of RTT measurements andthe second plurality of RTT measurements independently identify that themobile device is in the stopped state.
 4. The method of claim 1 furthercomprising collecting movement data from a plurality of data sources;wherein determining that the mobile device is in the stopped statecomprises determining that a threshold number of the plurality of datasources and the plurality of RTT measurements identify the mobile deviceas in the stopped state.
 5. The method of claim 1 wherein determiningthat the mobile device is in the stopped state further comprisesfiltering the plurality of RTT measurements between the mobile deviceand the at least one AP.
 6. The method of claim 5 wherein the pluralityof RTT measurements are filtered using a free particle filter.
 7. Themethod of claim 1 wherein the determining whether the mobile device isin the stopped state is further based at least in part on at least oneglobal navigation satellite service (GNSS) measurement.
 8. The method ofclaim 1 wherein the determining whether the mobile device is in thestopped state is further based at least in part on received signalstrength indication (RSSI) measurements between the mobile device andthe at least one AP.
 9. The method of claim 8 wherein the determiningwhether the mobile device is in the stopped state is further based on ananalysis of a correlation between the RSSI measurements and theplurality of RTT measurements.
 10. The method of claim 9 wherein thedetermining whether the mobile device is in the stopped state is furtherbased at least in part on sensor data from an accelerometer of themobile device during a first time period.
 11. The method of claim 10wherein the determining whether the mobile device is in the stoppedstate is further based on an output of a Kalman filter using the sensordata, the RSSI measurements, and the plurality of RTT measurements. 12.The method of claim 1 wherein determining that the mobile device is inthe stopped state comprises determining, based at least in part on theplurality of RTT measurements, that a position of the mobile deviceremains within a threshold area during a first period of time.
 13. Themethod of claim 12 wherein the threshold area is based at least in parton a known noise value associated with RTT measurements involving the atleast one AP.
 14. The method of claim 12 wherein the threshold area isassociated with a predetermined displacement value.
 15. The method ofclaim 14 wherein the predetermined displacement value is 5 cm.
 16. Themethod of claim 14 wherein the predetermined displacement value isreceived as a user input at the mobile device; and wherein thepredetermined displacement value is 5 m.
 17. The method of claim 1further comprising: initiating collection of the plurality of RTTmeasurements in response to a signal from a tracking device that isseparate from the mobile device.
 18. The method of claim 17 furthercomprising: receiving, at the tracking device, a request for the stoppedstate from a position tracking management entity; and communicating thesignal from the tracking device to the mobile device in response toreceiving the request for the stopped state.
 19. A mobile devicecomprising: means for collecting a plurality of round trip time (RTT)measurements between the mobile device and at least one access point(AP); means for analyzing the plurality of RTT measurements; and meansfor determining that the mobile device is in a stopped state, including:analyzing the plurality of RTT measurements between the mobile deviceand the at least one AP; and determining that a change in measured RTTis below a predetermined threshold for a first period of time.
 20. Themobile device of claim 19 further comprising: means for collecting aplurality of movement measurements in addition to the plurality of RTTmeasurements; and means for filtering the plurality of RTT measurementsand the plurality of movement measurements.
 21. The mobile device ofclaim 20 further comprising: means for communicating results of thedetermining that the mobile device is in the stopped state to a user.22. A mobile device comprising: a processor; a wireless transceivercoupled to the processor; and a memory coupled to the processor andcomprising a round trip time (RTT) positioning module which causes theprocessor to: collect a plurality of round trip time (RTT) measurementsbetween the mobile device and at least one access point (AP); anddetermine that the mobile device is in a stopped state, including:analyzing the plurality of RTT measurements between the wirelesstransceiver and the at least one AP; and determining that a change inmeasured RTT is below a predetermined threshold for a first period oftime.
 23. The mobile device of claim 22 further comprising: a user inputmodule connected to the processor, wherein the RTT positioning modulefurther causes the processor to: display a user interface on the mobiledevice; and accept a user selected threshold via the user interface. 24.The mobile device of claim 23 wherein the RTT positioning module furthercauses the processor to: initiate collection of the plurality of RTTmeasurements in response to a request from an application module for thestopped state.
 25. A non-transitory computer-readable instruction mediumcomprising instructions that, when executed by a processor coupled tothe non-transitory computer-readable instruction medium, cause a mobiledevice comprising the processor to: collect a plurality of round triptime (RTT) measurements between the mobile device and at least oneaccess point (AP); and determine that the mobile device is in a stoppedstate, including: analyzing the plurality of RTT measurements betweenthe mobile device and the at least one AP; and determining that a changein measured RTT is below a predetermined threshold for a first period oftime.
 26. The non-transitory computer-readable instruction medium ofclaim 25 wherein the instructions further cause the mobile devicecomprising the processor to: identify a plurality of APs; and select theat least one AP from the plurality of APs.
 27. The non-transitorycomputer-readable instruction medium of claim 26 wherein the at leastone AP is selected from the plurality of APs based on a signal qualityof the at least one AP.
 28. The non-transitory computer-readableinstruction medium of claim 26 wherein the at least one AP is selectedfrom the plurality of APs based on a position of the at least one AP.29. The non-transitory computer-readable instruction medium of claim 25wherein the plurality of RTT measurements between the mobile device andat least one AP are collected without determining a processing delayassociated with the AP.